The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Rix Racing
Please Support Morrison Fabrication

Overheating on the freeway? (Hi, I'm new)

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

pressf1forhelp

5+ Year Contributor
32
3
Nov 24, 2017
Oceanside, California
Hello fellow dsmers! I have acquired a 97 Eclipse GST and have owned it for about 8 months now. Please excuse my long post, but the more you know is probably for the best.

Car History:

This car had two previous owners. Some guy bought it back in 97 and put 100k (bought the car with 165k and I've put 13k on it) and then decided to garage it for 5 years. He called up his cousin (the man I purchased the vehicle from) and basically told him if he could get it in running condition the car was his. Now its my little gem in my life and is close to immaculate condition. Car runs beautifully and pulls really nicely. Both of the previous owners were mechanics, so when I bought the car a lot was done to it. All listed below was done by the seller himself (so no records, but I've maintained plenty of cars myself so I took a good look for any bs):

-New clutch and flywheel (new meaning new not resurfaced)
-4 New tires, rotors (again, not resurfaced) and brake pads.
-New front axle and tie rods
-Full exhaust and intake system
- -Insert generic spring and shock set here-
- Recently replaced the oil pan gasket and a motor mount (done at a shop, my new landlord is not very fond of me doing repairs in my car port)
- Everything else to my knowledge is stock
My current to do list:

-Upstream 02 sensor is dead (check the CEL code)
-Cat is most likely on its way out
-Intake system is most likely not street legal
-Timing belt in the next couple of months
-All of the above made my car not pass smog...but you know how that goes. *cough* *cough*

Anyways, on to the topic of my post.

So two days ago I'm driving my normal commute to work and I look at my gauges (as I do constantly) and my temperature was up 1/4 past normal operating temperatures. I was traveling 75-80 MPH with very little boost pressure built up. I get off the freeway and travel to work and strangely the temperature begins to fall back to normal operating temperature as I drive on surface streets (WTF?).

Things I've done to try to diagnose the problem over the past 3 days:

-Checked the rad cap which seems pretty aged (will replace asap)
-While the cap was off, I squeezed the rad-thermostat housing hose to see if I had air in the system or not. Seemed like there was a very minuscule amount that I was able to bleed out with my quick fix.
-Ran the heater to check for smells when the temp. rose and smelled nothing funny but did notice that the higher the gauge went the less heat I was receiving. The air was almost cool.
-Antifreeze seems dirty but not brown or discolored much

While idling the temperature sits nice and safe or like 2cm above. I'm clueless at this point. I'm thinking that the thermostat could possibly be seized but I wont be able to get in there until Monday. Any advice would be greatly appreciated. Sorry for the long post.
 
That would more than likely be the culprit behind the freeway overheating. Do a search on here regarding freeway overheating, and you will see the fixes that will help. Basically...the FMIC becomes an obstruction for airflow to hit the radiator, which in turn causes temps to go up. To help lower the temps, you can find numerous fixes to help with this, some will be more beneficial than others, but you may need to do more than 1. Start with proper ducting, which will "force" the air to have to go through the FMIC and to the radiator, without the air going around it, as air will take the path of least resistance. You can start by sealing the sides of the FMIC to the radiator using any combination of sheetmetal, foam, and/or heavy duty tape. Additionally, you can add some sort of air dam underneath the car to divert incoming air directly to the radiator. Other things that will help are exhaust wrap, turbo blanket, different fans, rad, etc. Start with the ducting though as its cheap and will definitely help, as well as making sure your fans are functioning when at idle.
 
Flush the cooling system and replace the thermostat. If your heater is not working it has nothing to do with having a front mount intercooler.

Your cooling system is having problems. Flush and thermostat will determine its.condition. It may be a coolant leak or a water pump issue as well

So take it up to the shop and ask for a coolant flush. You can replace the thermostat later in the parking lot yourself. Even if the land Lord isnt good about working on cars you can always load up your tools and work on the car in the parking lot at the Auto parts store
 
Last edited:
If your temps are rising while on the highway you likely have air in the system.

Flush the system and when you refill it, take the time to bleed all of the air out. Let it warm up and idle until the fans kick on. After you think it's good, take it for a drive so it can go through a full heat cycle and then top off the coolant when you get back from the drive.
 
Hello fellow dsmers! I have acquired a 97 Eclipse GST and have owned it for about 8 months now. Please excuse my long post, but the more you know is probably for the best.

Car History:

This car had two previous owners. Some guy bought it back in 97 and put 100k (bought the car with 165k and I've put 13k on it) and then decided to garage it for 5 years. He called up his cousin (the man I purchased the vehicle from) and basically told him if he could get it in running condition the car was his. Now its my little gem in my life and is close to immaculate condition. Car runs beautifully and pulls really nicely. Both of the previous owners were mechanics, so when I bought the car a lot was done to it. All listed below was done by the seller himself (so no records, but I've maintained plenty of cars myself so I took a good look for any bs):

-New clutch and flywheel (new meaning new not resurfaced)
-4 New tires, rotors (again, not resurfaced) and brake pads.
-New front axle and tie rods
-Full exhaust and intake system
- -Insert generic spring and shock set here-
- Recently replaced the oil pan gasket and a motor mount (done at a shop, my new landlord is not very fond of me doing repairs in my car port)
- Everything else to my knowledge is stock
My current to do list:

-Upstream 02 sensor is dead (check the CEL code)
-Cat is most likely on its way out
-Intake system is most likely not street legal
-Timing belt in the next couple of months
-All of the above made my car not pass smog...but you know how that goes. *cough* *cough*

Anyways, on to the topic of my post.

So two days ago I'm driving my normal commute to work and I look at my gauges (as I do constantly) and my temperature was up 1/4 past normal operating temperatures. I was traveling 75-80 MPH with very little boost pressure built up. I get off the freeway and travel to work and strangely the temperature begins to fall back to normal operating temperature as I drive on surface streets (WTF?).

Things I've done to try to diagnose the problem over the past 3 days:

-Checked the rad cap which seems pretty aged (will replace asap)
-While the cap was off, I squeezed the rad-thermostat housing hose to see if I had air in the system or not. Seemed like there was a very minuscule amount that I was able to bleed out with my quick fix.
-Ran the heater to check for smells when the temp. rose and smelled nothing funny but did notice that the higher the gauge went the less heat I was receiving. The air was almost cool.
-Antifreeze seems dirty but not brown or discolored much

While idling the temperature sits nice and safe or like 2cm above. I'm clueless at this point. I'm thinking that the thermostat could possibly be seized but I wont be able to get in there until Monday. Any advice would be greatly appreciated. Sorry for the long post.
Check the coolant level when it's cold, is it full? Definitely change the radiator cap and flush the fluid. Properly burp the rad. If the car has been sitting for that long, could be some corrosion in the radiator and a new one may be necessary. The current temperature in NY is 40s 50s and my coolant temp stays at 195 190 with a vrsf with no ducting, during the summer it's a different story. I personally would just do a quick overhaul on the cooling system,new coolant,new cap, new thermostat,new radiator and burp the system.
 
FMIC VRSF....put a big air dam right under the radiator support. I have a write up. It pulls all of the air going around and under the fmic back up to the radiator. 80's Trans Am's had aluminum heads and if you tore up the air dam, it toasted the heads. Not cooling good enuf. I have a 3rd gen F body airdam on my E85 Sleeper DSM and it works great at scooping up air. :sneaky: @ErikTande has some great help on this. Look up his articles. :thumb:
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top